Simplify the following expression: $k = \dfrac{3a^2 + a}{6a^2 + 5ba} - \dfrac{6a^2 - ba}{6a^2 + 5ba}$ You can assume $a,b,c \neq 0$.
Solution: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{3a^2 + a - (6a^2 - ba)}{6a^2 + 5ba}$ $k = \dfrac{-3a^2 + a + ba}{6a^2 + 5ba}$ The numerator and denominator have a common factor of $a$, so we can simplify $k = \dfrac{-3a + 1 + b}{6a + 5b}$